Take Foster to 87th. Take 87th North and follow the bike path signs. Keep following the signs until you get to Caruthers (just north of Division). Take the bike path north until you get to Burnside. Take Burnside west till you get to 71st. Turn right and follow the bike path signs to Davis, Everett, and Ankeny. Take Ankeny to 12st and then you have choices between taking the Burnside Bridge over to downtown or going to the Steel Bridge.